At present, with the continuous expansion of the Wireless Local Area Networks (WLAN) industry, the load of a WLAN network is also increasing. Moreover, with the increase in the number of users, a dense network scenario results in a significant drop in network efficiency of the WLAN. Simply increasing a transmission rate does not solve this problem. The multi-user parallel transmission serves as an alternative technology to ensure the network efficiency, which has drawn great attention and research.
In the related art, the multi-user parallel transmission technology includes, for example, a Multi-User Multiple-Input Multiple-Output (MU-MIMO) technology and an Orthogonal Frequency Division Multiple Access (OFDMA) technology. As for the MU-MIMO technology where, multiple layers of MIMO are distributed to multiple stations, a spatial multiplexing technology is used to improve time and frequency utilization rates. The introduction of the OFDMA technology enables multiple stations to perform frequency-division-multiplexing across the entire bandwidth, not only to utilize the selection of frequencies of the stations to better increase the frequency utilization rate, but also to reduce a proportion of an overhead in contending resources for small packet transmissions to an overhead for the entire transmission to increase the time utilization rate.
Multiple non-AP STAs (Stations) in the WLAN transmit data to an access point (AP) at the same time, which is generally referred to as uplink multi-user (UL MU) transmission, where a user is equivalent to a station. Or, the AP simultaneously transmits data to the multiple non-AP STAs, which is referred to as downlink multi-user (DL MU) transmission. A typical frame exchange sequence for the uplink/downlink multi-user transmission is as shown in FIG. 1.
The UL MU transmission requires the AP to perform uplink resource allocation and trigger uplink synchronous transmission in a manner of transmitting a trigger frame or carrying a trigger information field in a radio frame. The trigger frame or trigger information field carries scheduling information of the station, such as identification information of the station, information of time and frequency resources used in uplink transmission of the station, time-frequency offset calibration information of the station. After the AP transmits the trigger frame or the trigger information field, the station receives the trigger frame or trigger information field. If the identification information of the station is carried in the trigger frame or trigger information field, this station is scheduled in this UL MU transmission. If the station has data to be transmitted, the station performs preparation, synchronization according to the time-frequency offset calibration information indicated by the AP, and transmission on allocated time and frequency resources.
In the related art, when a STA adds a traffic stream with an AP, the STA negotiate with the AP to determine its own access approach, which is one of a scheduling access mechanism, a EDCA mechanism, and a hybrid access mechanism of the two mechanisms. In the above process where the AP triggers the uplink synchronous transmission, the access approach employed by the station is the scheduling access mechanism. Before the AP transmits the trigger frame, the STA report a situation about its own buffer, the AP will allocate resources according to the received situation about the buffer of the station and schedule the station to transmit uplink data for one or more times. When the AP schedules resources for the STA, the AP may update the status of the buffer of the corresponding station in real time according to the scheduling information.
However, if the STA employs the EDCA mechanism to transmit data in a process of waiting for being scheduled by the AP, the AP does not obtain a message in real time, and may not update the status of the buffer of the corresponding STA in real time, resulting in inaccuracy in subsequent scheduling of the AP, and even empty scheduling and waste of the resources. Although the above problem can be solved by the station reporting the situation about its own buffer in real time, the real-time reporting of the situation about its own buffer will greatly increase the network load. In addition, when the access approach of the station changes, it is necessary to cut off the added traffic stream connection, and then add a traffic stream and negotiate with the AP again. Such an updating manner is not flexible and reduces the efficiency of the MAC layer. Accordingly, how to improve the utilization rate of resources and the efficiency of the MAC layer is an urgent issue to be solved.